Conventionally, there has been used a plasma processing apparatus for performing plasma processing on a substrate such as a semiconductor wafer or a substrate for a liquid crystal display (LCD). For example, in a manufacturing process of a semiconductor device, a plasma etching processing apparatus is being used to etch and remove an oxide film or the like formed on a semiconductor wafer serving as a substrate to be processed, thereby forming a fine electric circuit on the semiconductor wafer.
In the plasma processing apparatus, the semiconductor wafer is mounted on an upper surface of a lower electrode (susceptor) disposed in an airtightly sealed processing chamber. There have been known various types of means for generating a plasma in a processing chamber. For example, in an apparatus for generating a plasma by supplying a radio frequency (RF) power to a pair of parallel plate electrodes which are vertically provided to face each other, an upper electrode is disposed to face a lower electrode in a processing chamber. When a RF power is applied to one or both of the upper and lower electrodes, a plasma is generated in the processing chamber and etching is performed by the plasma (see, e.g., Patent Documents 1 to 3).
[Patent Document 1] Japanese Patent Laid-open Application No. 2004-95909
[Patent Document 2] Japanese Patent Laid-open Application No. 2005-236138
[Patent Document 3] Japanese Patent Laid-open Application No. 2006-165093
However, a lower surface of the upper electrode, a peripheral surface of the lower electrode and the like are exposed to the plasma generated in the processing chamber during the plasma processing. The upper and lower electrodes are made of conductive metal such as aluminum, and the metal exposed to the plasma may cause contamination. Accordingly, a protection member such as quartz is attached to the lower surface of the upper electrode, the peripheral surface of the lower electrode and the like. In this case, conventionally, the protection member is attached to the lower surface of the upper electrode, the peripheral surface of the lower electrode and the like by using screws made of heat resistant plastic such as Vespel (registered trademark) or the like.
In the meantime, there is a need to adjust the semiconductor wafer mounted on the lower electrode to have a desired temperature during the plasma processing. In this case, the lower electrode is first adjusted to a desired temperature, and then heat is transferred to the semiconductor wafer in order to adjust the temperature of the semiconductor wafer. Further, in order to maintain the temperature of the semiconductor wafer at the desired temperature, the upper electrode or the like is also adjusted to a desired temperature. Moreover, the plasma generated in the processing chamber or the like increases the temperature of a wall surface of the processing chamber, the upper electrode, or the like. In this manner, the temperatures of various components such as the upper electrode, the lower electrode and the like in the plasma processing apparatus are changed due to the plasma processing.
However, the respective components of the plasma processing apparatus are not formed of a same material, and each component is made of a material selected according to its use. For example, as described above, although the upper and lower electrodes are made of metal such as aluminum or the like, the protection members attached to their surfaces are made of quartz or the like. Accordingly, the respective components of the plasma processing apparatus have different linear expansion coefficients and receive thermal stress due to the change of temperature during the plasma processing.
Further, the thermal stress causes damage to the respective components of the plasma processing apparatus or the coupling members such as screws fixing the respective components due to the thermal stress. Further, the respective components may be deformed even though they are not damaged.